The present invention relates a method for depositing an indium oxide or an indium tin oxide thin film on a polymer substrate, and more particularly, to a process in which a surface of a polymer substrate is modified by using an ion beam having an energy and a transparent and conductive indium oxide or indium tin oxide thin film is deposited thereon by an ion assisted deposition and/or an ion beam sputtering method.
A transparent conductive thin film is electrically conductive and has a high transparency in a visible ray.
By using such inherent property, the transparent conductive thin film is adopted to various fields such as an antistatic film in the optical field such as a Braun tube or glasses, an electrode of an LCD or semiconductors, electrode of solar battery or gas sensor.
Up till now, as a substrate for depositing the transparent conductive thin film, glasses have been used, and in order to fabricate thin films on the glasses, various methods such as an RF-sputtering, a DC-sputtering, a thermal evaporation, a chemical vapor deposition (CVD) and sol-gel method have been used.
Recently, with the development of an electronic industry, products becomes compact and light rapidly. According to the tendency, attempts has proceeded to deposit the transparent conductive thin film on a polymer substrate instead of a glass substrate.
In case of using the polymer substrate instead of a glass substrate, there is advantages that a product can be light and is hardly broken. In addition, since the polymer substrate has a flexibility, it is possible to fabricate a flexible circuit board which would be easily carried.
However, in spite of such advantages, there are many restrictions to use the polymer substrate instead of the glass substrate.
For example, first since the polymer substrate has a low surface energy compared with the glass substrate, it has a weak adhesive force with respect to a thin film to be deposited thereon.
Accordingly, there have been many attempts to increase the surface energy of a polymer, for which plasma or a chemical processing method has been mostly used.
However, these methods have a problem that it does a big physical and chemical damage to the surface of the polymer, the transparency of a substrate is reduced or the adhesive characteristic is not much improved.
In addition, in case that the existing deposition method is used to fabricate the transparent conductive thin film on the polymer substrate, the substrate must be heated at more than 200xc2x0 C. However, this temperature range is higher than a melting point of the polymer, and then it is difficult to use the polymer as a substrate.
Therefore, an object of the present invention is to provide a method for depositing an indium oxide (IO) and an indium tin oxide (ITO), a transparent conductive thin film, at a low substrate temperature, especially at a room temperature, by using a processing method which does not do any damage to a transparency of a polymer substrate and a chemical stability of a surface-modified layer of a polymer substrate.
In order to achieve the above objects, there is provided a method for depositing an IO or an ITO thin film on a polymer substrate, in which oxygen or argon ion beam is applied on a polymer substrate with a certain acceleration energy to modify the surface of the polymer substrate, on which an IO or an ITO thin film is deposited while applying oxygen, argon or oxygen-argon mixed ion beam under vacuum.
In order to achieve the above objects, there is further provided a method for depositing an IO or an ITO thin film on a polymer substrate, including the steps of: applying oxygen or argon ion beam on the polymer substrate with a certain acceleration energy to modify a surface of the polymer substrate; generating an ion beam from a cold cathode ion source by using argon, oxygen or its mixture gas under vacuum; sputtering the ion beam to a target substance consisting of In2O3 or In2O3 and SnO2; and depositing an IO or the ITO thin film on the surface-modified polymer substrate.